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Crystal growth and characterization studies of SMHP single crystal in silica gel medium and laser induced nucleation reduction process
Biochemical Engineering Journal 35 (2007) 244–249
Crystal growth and characterization studies of SMHP single crystal in silica gel medium and laser induced nucleation reduction process P. Sundaramoorthi a,∗ , S. Kalainathan b a
Department of Physics, Mahendra Engineering College, Mallasamudram (W), Namakkal 637503, Tamilnadu, India b Department of Physics, Vellore Institute of Technology, Vellore 632014, Tamilnadu, India Received 7 June 2006; received in revised form 16 December 2006; accepted 20 December 2006
Abstract SMHP (strontium magnesium hydrogen phosphate) crystals were grown in silica gel medium in three growth environments using different gel densities, various concentrations of phosphoric acid and supernatant solutions. The gel pH plays an important role in the formation of different HPO4 species in the phosphoric system. The pH ranges in which HPO4 2− ion dominate were considered, which in turn is necessary for the growth of SMHP crystals. The SMHP crystals are grown in three different growth environments by applying various growth parameters and found the optimum growth environment. The characterization of grown crystals were studied by FTIR, TGA/DTA, SEM, XRD and etching. © 2007 Elsevier B.V. All rights reserved. Keywords: SMHP; Laser light; Calculi; Surface morphology; Growth parameters; Trace elements and isotopes
1. Introduction SHP (strontium hydrogen phosphate) and BHP (barium hydrogen phosphate) were grown in silica gel medium at room temperature and reported [1,2]. In present study, an approach is made to grow mixed crystal in silica gel medium at different environments, which contains one major element (phosphate), one minor or trace element (strontium) and one inhibitor (magnesium). SMHP is a mixed crystal, which typically represent the biological crystals formed in the human urinary tracts called renal stones. Strontium (Sr) is a silvery-white alkaline earth metal that exists in several stable radioactive isotopes (e.g. Sr89, Sr-90). Strontium is the fifteenth most abundant element in nature and it is the most abundant trace element in seawater and thus, it has been become incorporated into all plants and animal tissues. The daily intake of strontium varies from about 1.8 to 2.0 mg/day. Of this, a negligible quantity is supplied by air, approximately 90% by food and the remaining percent by water. Strontium is present naturally in many foods like spices, seafood, cereals, grains and leafy vegetables. There are some evidences that strontium is essential for the growth of animals,
∗
Corresponding author. Tel.: +91 4288 238888/238777; fax: +91 4288 238999. E-mail address: [email protected] (P. Sundaramoorthi). 1369-703X/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.bej.2006.12.027
especially for the calcification of bone and teeth. Metabolism of strontium closely resembles that of calcium, especially with regard to bone. The absorption of strontium normally varies from 5 to 25% in injected dose. A 70 kg standard man contains nearly 320 mg of strontium. The skeleton contains more than 99% of the strontium. The rest is distributed among soft tissues; the largest concentration resides in the aorta, larynx, trachea and lower gastrointestinal tract. When administrated orally, it is primarily excreted in the faeces. Strontium is excreted in low in the sweat and in the milk of lactating females. When the mineral level of the body fluid increases, automatic mineral deposition starts. Authors have done a series of experiments (in vivo studies) with silica gel as a biological crystal growth medium at different pH values ranging from 5.5 to 10 and have proved that one can obtain the periodic precipitation, Liesegang rings of biological crystals such as HAP, Brushite, Struvite, BMHP, SMHP, etc. [3–5]. 2. Materials and methods The dissociation of phosphoric acid system can be represented by three-dissociation equilibrium and the presence of various ions at various pH values are reported [6]. Based on the account of these results, the gel pH in the range from 6 to 10 has been used (Milwaukee QS-MN pH-600, packet digital pHmeter are used for measurements) in which the HPO4 2− ions
P. Sundaramoorthi, S. Kalainathan / Biochemical Engineering Journal 35 (2007) 244–249
Fig. 1. Growth of SMHP crystals within laboratory environment (SD) at 30 ◦ C (gel density = 1.03 gm/cm3 ).
dominates or alone exists. This decreases the possibility of the occurrences of SMP crystals during SMHP growth. The crystallization apparatus employed were glass test tube of 25 mm diameter and 150 mm length for single diffusion method (SD) and thick walled 30 mm diameter and 180 mm long glass U tubes for double diffusion (DD) method. The chemicals used were Excelar-Qualigens (E-Q) AR grade SrCl2 and Mg(NO3 )2 ·2H2 O (MW —258.41) and E-Q, AR grade phosphoric acid (Sp.gr.1.75). The SMS gel or water glass was prepared as per the literature [7]. One of the reactant phosphoric acid was mixed with silica gel at desired gel density and elevated temperatures. After the gel set, the supernatant solution (strontium chloride +magnesium nitrate) at a required mole solution was slowly added along the walls of the growth columns (test tubes, U tubes) over the set gels and tightly closed to prevent evaporation. Then the growth systems were allowed to react within the gel medium. The temperatures of the growth columns were maintained by the constant temperature bath continually. The sun light exposed medium, the exposure of sun light in to the SMHP growth medium was only in day time (special glass reflection arrangement in a squire box) that is only 8 h/day and the growth period was 3 months. In these investigations, semiconductor diode Laser were used as a one of the growth environment, the power out put was of 3 mW continuously .The Laser out put wavelength and frequencies were ˚ and 4.29 × 1014 Hz. The Laser light was applied to the 7000 A growth columns from top to bottom by SMPS arrangements.
245
Fig. 2. Growth of SMHP crystals within laboratory environment (SD) at 30 ◦ C (gel density = 1.04 gm/cm3 ).
3.1. FTIR spectral analysis of SMHP crystals FTIR spectrometer having KBr pellets sample holder and KBr detector was used for the analysis. The KBr pellet samples were used to record the spectrum and the absorption frequencies range from 600 to 4000 cm−1 . Fig. 8 shows the FTIR spectrum of SMHP crystals. The SMHP FTIR spectrum results matches with Socrater [8]. The absorption bonds, absorption frequencies and percentage of transmittance were recorded and compared with the reported values. The values are tabulated in Table 3. The frequencies values functional groups confirm the SMHP crystal constituents. 3.2. Thermo gravimetric (TGA/DTA) analysis of SMHP crystals The TGA and DTA of SMHP crystals were carried out by STA 11500-PLTS instruments. The SMHP crystal of 2.439 mg sample was taken for the TGA process. The TGA was started
3. Result and discussion The SMHP crystals are grown in three different growth faces by applying various growth parameters. Among them, the Laser exposed growth medium shows better nucleation reduction and no crystals were formed, because of the inability to attain super saturation. In sun light exposed medium partial nucleation was observed, since exposure of sun light to the growth medium was only in daytime that is only 8 h/day and the growth period was 3 months (Figs. 1–7, Tables 1 and 2).
Fig. 3. Growth of SMHP crystals SD process with the sun light exposed medium at 44 ◦ C.
246
P. Sundaramoorthi, S. Kalainathan / Biochemical Engineering Journal 35 (2007) 244–249
Fig. 6. Harvested SMHP crystals in SD process.
Fig. 4. Growth of SMHP crystals DD process within the laboratory medium at 30 ◦ C.
from room temperature to 1000◦ C by heating at a constant rate. Fig. 9 shows the TGA and DTA graph of SMHP crystals. The percentage of weights present in the SMHP sample at a particular temperature was tabulated in the Table 4 [10]. The TGA of SMHP crystals were liberating water molecules up to the temperature of 114 ◦ C and then phosphate atom decomposing up to 410 ◦ C. Remaining sample, which contain Sr, Mg that is stable compound with respect to the temperature up to 900 ◦ C (boiling points of the Sr, Mg compounds are above 1000 ◦ C). Twenty-nine percentages of SMHP crystals were decomposed below 900 ◦ C and 71% of the sample was found to be stable at 900 ◦ C. 3.3. Etching study of SMHP crystals A well-grown SMHP crystal was immersed in HCl solution at a desired concentration. The dissolution of SMHP crystal depends upon the etchant concentration, temperature, crystal morphology, etching time, etc. [13–16] .The etch pits are shown in Fig. 10. The etch pits observed in the grown SMHP crystals were found as helical pits, spiral pits, cone pit, leaf pit and step pits.
Fig. 5. Growth of SMHP crystal with Laser exposed medium in DD process (gel density = 1.04 kg/m3 , IR = 1N, pH = 6.8, gel setting time was 5 h, reaction period was 130 days).
Fig. 7. Harvested SMHP crystals in DD process.
P. Sundaramoorthi, S. Kalainathan / Biochemical Engineering Journal 35 (2007) 244–249
247
Fig. 8. FTIR spectrum of SMHP crystal. Table 1 Single diffusion growth process (reaction test tubes) Growth parameters Gel density (gm/cm3 )
Phosphoric acid concentration (inner reactant mixed with gel) (N)
Gel + HPO4 value
Gel setting time
Supernatant concentration SrCl2 + Mg (NO3 )2 ·2H2 O (M)
Nucleation observed (h)
1.03 1.03 1.03 1.03 1.03 1.03 1.03 1.03 1.04 1.04 1.04 1.04 1.04 1.04 1.04 1.04
1 1 1 1 1.5 1.5 1.5 1.5 1 1 1 1 2 2 2 2
6.4 6.8 6.9 7.3 6.6 6.9 7.1 8.0 6.3 6.8 6.9 7.4 6.6 6.9 7.1 7.5
26 h 16 h 6 min 18 h 28 h 1h 3h 46 h 34 h 6h 45 min 68 h 24 h 1h 12 h 48 h
1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1
16 17 32 89 26 16 46 66 12 22 28 68 13 10 24 72
Growth period (days)
Growth appearances inside the growth medium
136
GC, PC
90
GC
140
GC, PC
75
GC
Growth period (days)
GC: good crystals are observed; PC: poly crystals are observed; Bold value: optimum growth parameters. Table 2 Double-diffusion growth process (U tubes) Growth parameters Gel density (gm/cm3 )
Phosphoric acid concentration (inner reactant mixed with gel) (N)
Gel + HPO4 pH value
Gel setting time
Supernatant concentration SrCl2 + Mg (NO3 )2 ·2H2 O (M)
Nucleation observed (h)
1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.04 1.04 1.04 1.04 1.04 1.04 1.04 1.04
1 1 1 1 2 2 2 2 1 1 1 1 2 2 2 2
6.0 6.5 6.9 7.1 6.4 6.9 7.2 8.1 6.2 6.8 7.2 7.6 6.2 6.9 7.5 7.9
48 h 16 h 15 min 26 h 36 h 4h 1h 98 h 46 h 5h 30 min 28 h 88 h 1h 10 h 58 h
1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1
45 26 22 90 20 22 86 98 40 22 64 88 20 10 32 82
GC: good crystals are observed; PC: poly crystals are observed; Bold value: optimum growth parameters.
Growth appearances
90
GC
70
GC, PC
110
90
GC
GC, PC
248
P. Sundaramoorthi, S. Kalainathan / Biochemical Engineering Journal 35 (2007) 244–249
Table 3 FTIR spectral analysis of SMHP crystal [9–12] S. no.
Composition/bond
Absorption frequency reported value (cm−1 )
Absorption frequency observed values (cm−1 )
Transmittance (%)
1
Sr, magnesium & hydrogen O–H symmetric, asymmetric (in plane)
3477–3207
2801 3555 3490 3318
33 20 18 21
2
O–H out of plane
745
792
43
3
PO4 group
1000–1100
1134 1055 988
15 15 35
4
Magnesium/appetite group
600–1010 (high frequency)
526 577 1066
22 32 15
5
C–C bond (unwanted)
885
899
46
Table 4 Thermal Analysis of SMHP crystals Points
1 2 3 4 5
Fig. 9. Show the thermo gravimetric spectrum of (TGA/DTA) SMHP crystals.
3.4. SEM studies of SMHP crystals A well-grown SMHP single crystal was selected for the investigation of surface morphology by SEM. The SEM photograph was made in the version S-300-I instrument. The sample named VCA-600 was kept in lobe middle and the data size was 640 × 480.The minor and major magnification of SEM was about 250 times. SEM acceleration voltage used was 25,000 V,
DTA (◦ C)
TGA Temperature (◦ C)
Percentage of SMHP crystal present
35 114 179 410 850
100 102 77 71 71
114.81 160.60 231.45 672.51 691.53
the sample was kept in a high vacuum at 18,200 m working distance, and monochromatic color mode was employed. Two hundred micrometers focusing of SMHP crystal SEM is shown in Fig. 11. In the surface analysis of SEM–SMHP crystal, few smooth surfaces, many fine grain boundaries and some valley regions were observed [17–20]. 3.5. X-ray diffraction of SMHP crystal The XRD results revealed the crystalline property of crystal. The XRD pattern and diffraction indices of the SMHP crystals
Fig. 10. Chemical etching of SMHP crystal at room temperature (30 ◦ C) [HCL as an etchant, etching time was 5 min, etchant normality was 2N].
P. Sundaramoorthi, S. Kalainathan / Biochemical Engineering Journal 35 (2007) 244–249
249
graph. The percentage loss of grown crystals was recorded in TGA/DTA analysis. XRD data of the crystal confirmed that the SMHP grown crystal system was triclinic structure. References
Fig. 11. SEM picture of SMHP crystals.
were recorded. Using the programme (Proszki) the lattice parameters of the SMHP crystal were calculated. The lattice ˚ b = 10.21 A, ˚ c = 10.58 A, ˚ α = 90◦ 18 , parameters are a = 10.02 A, ◦ ◦ β = 90 02 , γ = 90 08 . ˚3 The volume of the unit cell of the SMHP crystal is 1082.8 A Then one can identify and confirmed the SMHP crystal system is triclinic [21]. 4. Conclusion The crystal structure, growth morphology, chemical constituents, surface morphology and TGA/DTA analysis of strontium hydrogen phosphate (SMHP) crystals have been investigated. The SMHP crystals are grown in three different growth faces and found the optimum growth environment. FTIR spectrum was recorded and the functional group frequencies of SMHP crystal were analyzed, which confirm the SMHP chemical constituents. Chemical etching studies were carried out at room temperature and the etch pits are identified. The surface morphology of grown crystal was recorded using SEM photo-
[1] P. Sundaramoorthi, et al., Proceeding of the National Conference on Recent Trends in Material Science and Technology, 2005, p. 72. [2] P. Sundaramoorthi, et al., Proceeding of the Tenth National Seminar on Crystal Growth, 2005, p. 31. [3] P. Sudaramoorthi, et al., Asian J. Chem. 19 (2007) 2783–2791. [4] H.K. Hnisch, J.M. Garcia-Ruiz, J. Cryst. Growth 75 (1986) 195. [5] H.K. Hnisch, J.M. Garcia-Ruiz, J. Cryst. Growth 75 (1985) 203. [6] R.L. Pecsok, L.D. Shields, T. Cairns, I.G. McWillian, Modern Methods of Chemical Analysis, John Willy & Sons Inc., New York, 1976, pp. 438–442. [7] H.K. Henisch, Crystals in Gel and Liesegang Rings, Cambridge University Press, Cambridge, 1986, p. 11. [8] G. Socrater, Infrared Cha Group Friq, John Willy Ed., Chichester, 1980. [9] E. Hatscheck, J. Kollid Z. 37 (1936) 297. [10] C. Year, et al., J. Urology 86 (1961) 838–854. [11] C.M. Corns, J. Ann. Clin. BioChem. 20 (1983) 20–35. [12] A. Hesse, D. Bach, Stone analysis by infrared, spectroscopy, in: Alan Rose (Ed.), Urinary Stones, Clinical and Laboratory Aspects, University Park Press, Baltimore, 1982, pp. 87–105. [13] J.J. Gilman, J. Johnsion, G.W. Sears, J. App. Phys. 29 (1958) 749. [14] J.J. Gilman, et al., J. App. Phys. 27 (1956) 1018. [15] J.C. Fisher, Dissolutions and Mechanical Properties of Crystals, John Wiley and Sons Ed., New York, 1957. [16] J.B. New Kirk, Director Observation of Imperfection in Crystals, Interscience Publishers, New York, 1962. [17] K.J. Taukamot, J. Cryst. Growth 61 (1983) 199. [18] H.C. Gates, Thirty years of progress in Surface Science, in: Crystal Growth and Characterization, North Holland, 1975. [19] H. Bethage, et al., Electron Microscopy in Solid State Physics, Elsever Ed., Amsterdam, 1987. [20] N. Albon, et al., Growth and Perfection of Crystals, John Wiley Ed., New York, 1958. [21] G. Machennan, C.A. Reevers, J. Acta Cryst. 8 (1955) 579.
Crystal growth and characterization studies of SMHP single crystal in silica gel medium and laser induced nucleation reduction process P. Sundaramoorthi a,∗ , S. Kalainathan b a
Department of Physics, Mahendra Engineering College, Mallasamudram (W), Namakkal 637503, Tamilnadu, India b Department of Physics, Vellore Institute of Technology, Vellore 632014, Tamilnadu, India Received 7 June 2006; received in revised form 16 December 2006; accepted 20 December 2006
Abstract SMHP (strontium magnesium hydrogen phosphate) crystals were grown in silica gel medium in three growth environments using different gel densities, various concentrations of phosphoric acid and supernatant solutions. The gel pH plays an important role in the formation of different HPO4 species in the phosphoric system. The pH ranges in which HPO4 2− ion dominate were considered, which in turn is necessary for the growth of SMHP crystals. The SMHP crystals are grown in three different growth environments by applying various growth parameters and found the optimum growth environment. The characterization of grown crystals were studied by FTIR, TGA/DTA, SEM, XRD and etching. © 2007 Elsevier B.V. All rights reserved. Keywords: SMHP; Laser light; Calculi; Surface morphology; Growth parameters; Trace elements and isotopes
1. Introduction SHP (strontium hydrogen phosphate) and BHP (barium hydrogen phosphate) were grown in silica gel medium at room temperature and reported [1,2]. In present study, an approach is made to grow mixed crystal in silica gel medium at different environments, which contains one major element (phosphate), one minor or trace element (strontium) and one inhibitor (magnesium). SMHP is a mixed crystal, which typically represent the biological crystals formed in the human urinary tracts called renal stones. Strontium (Sr) is a silvery-white alkaline earth metal that exists in several stable radioactive isotopes (e.g. Sr89, Sr-90). Strontium is the fifteenth most abundant element in nature and it is the most abundant trace element in seawater and thus, it has been become incorporated into all plants and animal tissues. The daily intake of strontium varies from about 1.8 to 2.0 mg/day. Of this, a negligible quantity is supplied by air, approximately 90% by food and the remaining percent by water. Strontium is present naturally in many foods like spices, seafood, cereals, grains and leafy vegetables. There are some evidences that strontium is essential for the growth of animals,
∗
Corresponding author. Tel.: +91 4288 238888/238777; fax: +91 4288 238999. E-mail address: [email protected] (P. Sundaramoorthi). 1369-703X/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.bej.2006.12.027
especially for the calcification of bone and teeth. Metabolism of strontium closely resembles that of calcium, especially with regard to bone. The absorption of strontium normally varies from 5 to 25% in injected dose. A 70 kg standard man contains nearly 320 mg of strontium. The skeleton contains more than 99% of the strontium. The rest is distributed among soft tissues; the largest concentration resides in the aorta, larynx, trachea and lower gastrointestinal tract. When administrated orally, it is primarily excreted in the faeces. Strontium is excreted in low in the sweat and in the milk of lactating females. When the mineral level of the body fluid increases, automatic mineral deposition starts. Authors have done a series of experiments (in vivo studies) with silica gel as a biological crystal growth medium at different pH values ranging from 5.5 to 10 and have proved that one can obtain the periodic precipitation, Liesegang rings of biological crystals such as HAP, Brushite, Struvite, BMHP, SMHP, etc. [3–5]. 2. Materials and methods The dissociation of phosphoric acid system can be represented by three-dissociation equilibrium and the presence of various ions at various pH values are reported [6]. Based on the account of these results, the gel pH in the range from 6 to 10 has been used (Milwaukee QS-MN pH-600, packet digital pHmeter are used for measurements) in which the HPO4 2− ions
P. Sundaramoorthi, S. Kalainathan / Biochemical Engineering Journal 35 (2007) 244–249
Fig. 1. Growth of SMHP crystals within laboratory environment (SD) at 30 ◦ C (gel density = 1.03 gm/cm3 ).
dominates or alone exists. This decreases the possibility of the occurrences of SMP crystals during SMHP growth. The crystallization apparatus employed were glass test tube of 25 mm diameter and 150 mm length for single diffusion method (SD) and thick walled 30 mm diameter and 180 mm long glass U tubes for double diffusion (DD) method. The chemicals used were Excelar-Qualigens (E-Q) AR grade SrCl2 and Mg(NO3 )2 ·2H2 O (MW —258.41) and E-Q, AR grade phosphoric acid (Sp.gr.1.75). The SMS gel or water glass was prepared as per the literature [7]. One of the reactant phosphoric acid was mixed with silica gel at desired gel density and elevated temperatures. After the gel set, the supernatant solution (strontium chloride +magnesium nitrate) at a required mole solution was slowly added along the walls of the growth columns (test tubes, U tubes) over the set gels and tightly closed to prevent evaporation. Then the growth systems were allowed to react within the gel medium. The temperatures of the growth columns were maintained by the constant temperature bath continually. The sun light exposed medium, the exposure of sun light in to the SMHP growth medium was only in day time (special glass reflection arrangement in a squire box) that is only 8 h/day and the growth period was 3 months. In these investigations, semiconductor diode Laser were used as a one of the growth environment, the power out put was of 3 mW continuously .The Laser out put wavelength and frequencies were ˚ and 4.29 × 1014 Hz. The Laser light was applied to the 7000 A growth columns from top to bottom by SMPS arrangements.
245
Fig. 2. Growth of SMHP crystals within laboratory environment (SD) at 30 ◦ C (gel density = 1.04 gm/cm3 ).
3.1. FTIR spectral analysis of SMHP crystals FTIR spectrometer having KBr pellets sample holder and KBr detector was used for the analysis. The KBr pellet samples were used to record the spectrum and the absorption frequencies range from 600 to 4000 cm−1 . Fig. 8 shows the FTIR spectrum of SMHP crystals. The SMHP FTIR spectrum results matches with Socrater [8]. The absorption bonds, absorption frequencies and percentage of transmittance were recorded and compared with the reported values. The values are tabulated in Table 3. The frequencies values functional groups confirm the SMHP crystal constituents. 3.2. Thermo gravimetric (TGA/DTA) analysis of SMHP crystals The TGA and DTA of SMHP crystals were carried out by STA 11500-PLTS instruments. The SMHP crystal of 2.439 mg sample was taken for the TGA process. The TGA was started
3. Result and discussion The SMHP crystals are grown in three different growth faces by applying various growth parameters. Among them, the Laser exposed growth medium shows better nucleation reduction and no crystals were formed, because of the inability to attain super saturation. In sun light exposed medium partial nucleation was observed, since exposure of sun light to the growth medium was only in daytime that is only 8 h/day and the growth period was 3 months (Figs. 1–7, Tables 1 and 2).
Fig. 3. Growth of SMHP crystals SD process with the sun light exposed medium at 44 ◦ C.
246
P. Sundaramoorthi, S. Kalainathan / Biochemical Engineering Journal 35 (2007) 244–249
Fig. 6. Harvested SMHP crystals in SD process.
Fig. 4. Growth of SMHP crystals DD process within the laboratory medium at 30 ◦ C.
from room temperature to 1000◦ C by heating at a constant rate. Fig. 9 shows the TGA and DTA graph of SMHP crystals. The percentage of weights present in the SMHP sample at a particular temperature was tabulated in the Table 4 [10]. The TGA of SMHP crystals were liberating water molecules up to the temperature of 114 ◦ C and then phosphate atom decomposing up to 410 ◦ C. Remaining sample, which contain Sr, Mg that is stable compound with respect to the temperature up to 900 ◦ C (boiling points of the Sr, Mg compounds are above 1000 ◦ C). Twenty-nine percentages of SMHP crystals were decomposed below 900 ◦ C and 71% of the sample was found to be stable at 900 ◦ C. 3.3. Etching study of SMHP crystals A well-grown SMHP crystal was immersed in HCl solution at a desired concentration. The dissolution of SMHP crystal depends upon the etchant concentration, temperature, crystal morphology, etching time, etc. [13–16] .The etch pits are shown in Fig. 10. The etch pits observed in the grown SMHP crystals were found as helical pits, spiral pits, cone pit, leaf pit and step pits.
Fig. 5. Growth of SMHP crystal with Laser exposed medium in DD process (gel density = 1.04 kg/m3 , IR = 1N, pH = 6.8, gel setting time was 5 h, reaction period was 130 days).
Fig. 7. Harvested SMHP crystals in DD process.
P. Sundaramoorthi, S. Kalainathan / Biochemical Engineering Journal 35 (2007) 244–249
247
Fig. 8. FTIR spectrum of SMHP crystal. Table 1 Single diffusion growth process (reaction test tubes) Growth parameters Gel density (gm/cm3 )
Phosphoric acid concentration (inner reactant mixed with gel) (N)
Gel + HPO4 value
Gel setting time
Supernatant concentration SrCl2 + Mg (NO3 )2 ·2H2 O (M)
Nucleation observed (h)
1.03 1.03 1.03 1.03 1.03 1.03 1.03 1.03 1.04 1.04 1.04 1.04 1.04 1.04 1.04 1.04
1 1 1 1 1.5 1.5 1.5 1.5 1 1 1 1 2 2 2 2
6.4 6.8 6.9 7.3 6.6 6.9 7.1 8.0 6.3 6.8 6.9 7.4 6.6 6.9 7.1 7.5
26 h 16 h 6 min 18 h 28 h 1h 3h 46 h 34 h 6h 45 min 68 h 24 h 1h 12 h 48 h
1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1
16 17 32 89 26 16 46 66 12 22 28 68 13 10 24 72
Growth period (days)
Growth appearances inside the growth medium
136
GC, PC
90
GC
140
GC, PC
75
GC
Growth period (days)
GC: good crystals are observed; PC: poly crystals are observed; Bold value: optimum growth parameters. Table 2 Double-diffusion growth process (U tubes) Growth parameters Gel density (gm/cm3 )
Phosphoric acid concentration (inner reactant mixed with gel) (N)
Gel + HPO4 pH value
Gel setting time
Supernatant concentration SrCl2 + Mg (NO3 )2 ·2H2 O (M)
Nucleation observed (h)
1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.04 1.04 1.04 1.04 1.04 1.04 1.04 1.04
1 1 1 1 2 2 2 2 1 1 1 1 2 2 2 2
6.0 6.5 6.9 7.1 6.4 6.9 7.2 8.1 6.2 6.8 7.2 7.6 6.2 6.9 7.5 7.9
48 h 16 h 15 min 26 h 36 h 4h 1h 98 h 46 h 5h 30 min 28 h 88 h 1h 10 h 58 h
1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1
45 26 22 90 20 22 86 98 40 22 64 88 20 10 32 82
GC: good crystals are observed; PC: poly crystals are observed; Bold value: optimum growth parameters.
Growth appearances
90
GC
70
GC, PC
110
90
GC
GC, PC
248
P. Sundaramoorthi, S. Kalainathan / Biochemical Engineering Journal 35 (2007) 244–249
Table 3 FTIR spectral analysis of SMHP crystal [9–12] S. no.
Composition/bond
Absorption frequency reported value (cm−1 )
Absorption frequency observed values (cm−1 )
Transmittance (%)
1
Sr, magnesium & hydrogen O–H symmetric, asymmetric (in plane)
3477–3207
2801 3555 3490 3318
33 20 18 21
2
O–H out of plane
745
792
43
3
PO4 group
1000–1100
1134 1055 988
15 15 35
4
Magnesium/appetite group
600–1010 (high frequency)
526 577 1066
22 32 15
5
C–C bond (unwanted)
885
899
46
Table 4 Thermal Analysis of SMHP crystals Points
1 2 3 4 5
Fig. 9. Show the thermo gravimetric spectrum of (TGA/DTA) SMHP crystals.
3.4. SEM studies of SMHP crystals A well-grown SMHP single crystal was selected for the investigation of surface morphology by SEM. The SEM photograph was made in the version S-300-I instrument. The sample named VCA-600 was kept in lobe middle and the data size was 640 × 480.The minor and major magnification of SEM was about 250 times. SEM acceleration voltage used was 25,000 V,
DTA (◦ C)
TGA Temperature (◦ C)
Percentage of SMHP crystal present
35 114 179 410 850
100 102 77 71 71
114.81 160.60 231.45 672.51 691.53
the sample was kept in a high vacuum at 18,200 m working distance, and monochromatic color mode was employed. Two hundred micrometers focusing of SMHP crystal SEM is shown in Fig. 11. In the surface analysis of SEM–SMHP crystal, few smooth surfaces, many fine grain boundaries and some valley regions were observed [17–20]. 3.5. X-ray diffraction of SMHP crystal The XRD results revealed the crystalline property of crystal. The XRD pattern and diffraction indices of the SMHP crystals
Fig. 10. Chemical etching of SMHP crystal at room temperature (30 ◦ C) [HCL as an etchant, etching time was 5 min, etchant normality was 2N].
P. Sundaramoorthi, S. Kalainathan / Biochemical Engineering Journal 35 (2007) 244–249
249
graph. The percentage loss of grown crystals was recorded in TGA/DTA analysis. XRD data of the crystal confirmed that the SMHP grown crystal system was triclinic structure. References
Fig. 11. SEM picture of SMHP crystals.
were recorded. Using the programme (Proszki) the lattice parameters of the SMHP crystal were calculated. The lattice ˚ b = 10.21 A, ˚ c = 10.58 A, ˚ α = 90◦ 18 , parameters are a = 10.02 A, ◦ ◦ β = 90 02 , γ = 90 08 . ˚3 The volume of the unit cell of the SMHP crystal is 1082.8 A Then one can identify and confirmed the SMHP crystal system is triclinic [21]. 4. Conclusion The crystal structure, growth morphology, chemical constituents, surface morphology and TGA/DTA analysis of strontium hydrogen phosphate (SMHP) crystals have been investigated. The SMHP crystals are grown in three different growth faces and found the optimum growth environment. FTIR spectrum was recorded and the functional group frequencies of SMHP crystal were analyzed, which confirm the SMHP chemical constituents. Chemical etching studies were carried out at room temperature and the etch pits are identified. The surface morphology of grown crystal was recorded using SEM photo-
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